The present invention concerns a process for upgrading hydrocarbonaceous oils. More specifically, the invention concerns a process for upgrading heavy oils by contacting the oils with free oxygen and liquid phase water at an elevated temperature.
Heavy petroleum fractions such as residuals and heavy crude oils can be used as low grade commercial fuels or may be converted by thermal and catalytic conversion processes into more valuable, lighter hydrocarbons, particularly gasoline. Heavy crudes and heavy oil fractions are often contaminated with substantial concentrations of detrimental materials. Common contaminants are organic nitrogen and sulfur compounds, metals, particularly nickel and vanadium, nondistillable, heat-sensitive coke precursors, such as asphatenes, and the like. When heavy oils are burned as fuel, combustion of the nitrogen and sulfur compounds results in formation of objectionable pollutants, nitrogen oxides and sulfur oxides. When heavy oils are upgraded by conventional catalytic conversions, the presence of the nitrogen and sulfur compounds, and particularly the presence of the metals, results in rapid deactivation of catalysts, and causes the upgrading of residual oils to be undesirably expensive. Conventional methods for upgrading heavy oil fractions to provide more valuable hydrocarbons often consume substantial amounts of hydrogen. The cost of hydrogen consumed is an economic drawback when hydroprocessing is employed for the upgrading. When upgrading of heavy crudes and oil fractions is carried out by means of coking, the presence of overly large concentrations of coke-forming materials, such as asphaltenes, results in lower yield of relatively more valuable distillate product and higher yield of relatively less valuable coke. Moreover, high sulfur concentration in the coke often makes it unsuitable for major applications, particularly electrode fabrication.
A general discussion of wet air oxidation technolgy, found in Mechanical Engineering, December 1979, page 30, is incorporated herein by specific reference. A discussion of regeneration of active carbon after use in waste water treating, by means of wet air oxidation, found in AICHE Symposium Series, Vol. 76, No. 192, (Recent Adances in Separation Technology - II), page 51 (AICHE, 1980), is incorporated herein by specific reference.
A process for removing pyritic sulfur from coal by treatment with water and air at elevated temperature and pressure to convert the pyritic sulfur to water-soluble ferrous and ferric sulfate is disclosed in U.S. Pat. No. 3,824,084. Use of silicates and an oxidizing agent (such as air, oxygen, hydrogen peroxide, alkali metal sulfides, alkaline or metal sulfides) or a reducing agent (such as H.sub.2, CO, K.sub.2, S.sub.2 O.sub.4, Nas.sub.2 O.sub.4, and alkali metal polythionates) in an aqueous medium to desulfurize coal is disclosed in U.S. Pat. No. 4,174,953 and U.S. Pat. No. 4,197,090.
Use of wet air oxidation to provide heat energy in the form of steam, as by wet oxidation of coal, is disclosed in U.S. Pat. No. 4,211,174, U.S. Pat. Nos. 4,100,730, and 4,013,560.
Use of copper or silver ions to catalyze wet air oxidation of organic material in waste water is disclosed in U.S. Pat. No. 3,912,626.
Treatment of papermill waste sludges to convert organic components to innocuous oxidation products and to provide for recovery of inorganic filter materials for reuse is disclosed in U.S. Pat. No. 3,876,497.
Essentially complete oxidation of solid or liquid combustible materials which are difficult to suspend in water, such as diesel fuel and nitroglycerine by direct injection into a wet air oxidation reactor is disclosed in U.S. Pat. No. 4,174,280.
None of the disclosures concerning wet air oxidation is concerned with upgrading of hydrocarbonaceous materials. Hydrocarbonaceous oils which are utilized in the disclosed wet air oxidation processes are simply essentially completely consumed to form highly oxidized materials, primarily carbon dioxide, water and the like.